I found this overview from Dr. William B. Grant to be extremely accurate,
correlating almost exactly with what I have observed and learned about air
pollution and forest health over the past 27 years.
Please give serious consideration to the implications of what he is
reporting.
- Gerry Hawkes - Woodstock, Vermont - ghawkes@sover.net
---------- Forwarded message ----------
Date: Sat, 1 Jun 1996 11:09:41 -0400 (EDT)
From: GRANT@vaxine.larc.nasa.gov
To: ghawkes@sover.net
Subject: Overview for the nets
June 1, 1996
A brief overview of the effects of air pollution (acid deposition and
ozone exposure) on trees and forests
by William B. Grant, PhD, 803 Marlbank Drive, Yorktown, VA
23692-4353, wbgrant@norfolk.infi.net
This is a short overview of the effects of air pollution on trees and
forests from the perspective of one who has only recently entered the
field from a background of atmospheric science.
The main atmospheric pollutants that affect trees and forests are nitrate,
sulfate, and ozone. In Europe, ammonium also contributes. Nitrate
comes from all hydrocarbon combustion, starting as nitric oxide (NO),
then oxidizing to become NO2, and NO3. Sulfur comes primarily from
coal combustion, but also from some oil/hydrocarbon combustion.
Ozone comes from photoproduction from the precursors, NOx and
hydrocarbons, thus also from combustion to a great extent. While
there are natural sources of ozone, background ozone levels are now 3-
4 times what they were at the end of the last century. Nitrates and
sulfates are deposited through rain and snow, as well as by dry
deposition and, at high elevation, through cloud mist.
Other aspects of air pollution that affect trees and forests are other
oxidants (nitrogen dioxide, sulfur dioxide), heavy metals,
chlorofluorocarbons through stratospheric ozone depletion and increased
UV-B radiation, carbon dioxide through climate modification, and
aerosols that reduce photosynthetically active radiation. These topics
have received less discussion in the literature than have acid and ozone,
but are found or thought to play roles in some cases.
Ozone enters tree leaves through the stomata, attacking the cells inside
the leaves. In response, photosynthesis rates are reduced (chlorophyll
is destroyed), more sugars are retained in the leaves, and less starch is
transported to the roots. As a result, insects are attracted to the leaves,
and the trees don't have enough starch reserves in the roots to survive
repeated defoliations. In addition, the trees cannot provide the
mycorrhizal fungi with the carbohydrates they require, and, thus, get
fewer base cations from the fungi.
Sulfate serves primarily to lower the soil pH, while nitrate not only
lowers the soil pH lower than sulfate can, but also acts as a nutrient,
stimulating tree growth, and leading to faster consumption and possible
depletion of base cations. Nitrate is able to lower soil pH to the point
where aluminum is brought into the Al3+ state in the soil solution,
where it then displaces base cations from the soil solution, and inhibits
the uptake of the base cations by the roots. Lower soil pH inhibits root
growth, making trees more susceptible to drought. In addition, the
excess nitrogen in the sap and leaves attracts insects. Note that
harvesting trees also leads to lower soil pH, since trees exchange a
hydronium ion for each base cation it takes from the soil. If the trees
do not decay and return the base cations to the soil, the pH levels
decline. In the southern U.S. pine forests, nitrate and sulfate
deposition and tree growth contribute about the same to soil
acidification.
One way trees fight disease is through compartmentalization, i.e.,
walling off injuries. However, with reduced calcium uptake, this
mechanism is compromised, making the trees more exposed to disease
and insects.
Acid deposition also makes trees less cold tolerant. Likely the
mechanisms include an alteration of the seasonal change cycles in the
trees due to excess nitrogen which stimulates growth, making them
unprepared for cold. However, it is a complex phenomenon.
Forest decline is a situation where tree growth is diminished, with, for
example, the canopy dominant trees having crown thinning or branches
without leaves, epicormic leaves, yellowing of leaves, etc. Increased
forest decline is often the first sign that a forest is in trouble due to air
pollution.
In summary, acid depositions and ozone exposures have increased
considerably in the past 50 years in Asia, Europe and the U.S., and
there have been many reports of tree/forest decline and increased
mortality. In general, the more highly polluted forests have the higher
rate of decline and mortality. In that regard, the red spruce dieback in
the U.S. is similar to the ozone hole over Antarctica: it occurred in the
region with conditions most favorable for a large effect - acid
depositions are greatest at the higher elevations due to increased
precipitation and cloud mist contact. As with stratospheric ozone
decreases which were eventually found worldwide, it is only a matter
of time until widespread decline in forest health will be found in the
entire eastern U.S. due to the combined effects of acid deposition and
ozone exposure. I predict that this time is not far off. I would
encourage forest researchers to look harder at forests in terms of air
pollution effects, perhaps mediated through reduced cold tolerance,
reduced reisitance to disease, drought, insect attacks and windfall.
How much longer can cold weather, disease, drought, insects, and
windfall, many of which have been around for millennia, be blamed for
forest decline when air pollution must be playing an important role?
I particularly admire the research done in Europe. It seems to me that
in Europe for one thing there is a tradition of sustainable agriculture.
For another, if air pollution is the cause of forest decline, the source
region may be another country. For a third, the scientists there seem
to be free to and encouraged to do good science.
At the end of this brief summary is a listing of 60 articles and books
that go into some of the points discussed here as well as document the
status of some forest decline in Europe and the U.S. While there is no
one publication that I want to single out, I think that the ensemble
paints a picture of the many effects of air pollution on trees and the
results in many forests which should give the concerned forested cause
for concern. These references are from those that I have assembled
over the past 14 months, primarily by obtaining them from the authors
or buying the books. I have over 1400 references included in my
bibliography, along with contact information for 517 corresponding
authors, which makes the literature accessible to anyone. I would be
happy to send the bibliography in WordPerfect 5.1 format on a 3.5"
disk to anyone who would like to have it. I would also welcome
additional articles and reports for my collection.
Selected bibliography
Aamlid, D., K. Venn, and A. O. Staunes, Forest decline in Norway:
Monitoring results, international links and hypotheses, Nor. J. Agric.
Sci., Suppl. 4, 1-27, 1990.
Aamlid, D., and K. Venn, Methods of monitoring the effects of air
pollution on forest and vegetation of eastern Finnmark, Norway, Nor.
J. Agric. Sci., 7, 71-87, 1993.
Aber, J. D., A. Magill, S. G. McNulty, R. D. Boone, K. J.
Nadelhoffer, M. Downs, and R. Hallett, Forest biogeochemistry and
primary production altered by nitrogen saturation, in press, 1996.
Anderson, R. L., P. Berrang, J. Knighten, K. A. Lawton, and K. O.
Britton, Pretreating dogwood seedlings with simulated acidic
precipitation increases anthracnose symptoms in greenhouse-laboratory
trials, Can. J. For. Res., 23, 55-58, 1993.
Bauce, E., and D. C. Allen, Role of Armillaria calvescens and
Glycobius speciosus in a sugar maple decline, Can. J. For. Res., 22,
549-552, 1992.
Bruck, R. I., Forest decline syndromes in the southeastern United
States, Ch. 4 in J. J. MacKenzie and M. T. El-Ashry, eds., Air
Pollution's Toll on Forests & Crops, Yale Univ. Press, New Haven,
113-190, 1989.
Bruck, R. I., W. P. Robarge, and A. McDaniel, Forest decline in the
boreal montane ecosystems of the southern Appalachian Mountains,
Water, Air, and Soil Pollution, 48, 161-180, 1989.
Cannon, W. N., Jr., Gypsy moth (Lepidoptera: Lymantriidae)
consumption and utilization of northern red oak and white oak foliage
exposed to simulated acid rain and ozone, Environ. Entomol., 22, 669-
673, 1993.
Chappelka, A. H., and P. H. Freer-Smith, Predisposition of trees by
air pollutants to low temperatures and moisture stress, Environ. Pollut.,
87, 105-117, 1995.
Cowling, E. B., Effects of air pollution on forests, J. Air Pollut.
Control Assoc., 35, 916-919, 1985.
de Steiguer, J. E., J. M. Pye, and C. S. Love, Air pollution damage to
U.S. forests, J. Forestry, 88, 17-22, Aug. 1990.
De Vries, W., E. E. J. M. Leeters, and C. M. A. Hendriks, Effects of
acid deposition on Dutch forest ecosystems, Water, Air and Soil
Pollut., 85, 1063-1068, 1995.
De Vries, W., M. Posch, T. Oja, H. van Oene, H. Kros, P.
Warfvinge, and P. A. Arp, Modelling critical loads for the Solling
spruce site, Ecological Modelling, 83, 283-293, 1995.
Eager, C., and M. B. Adams, eds., Ecology and Decline of Red
Spruce in the Eastern United States, Ecological Studies 96, Springer-
Verlag, New York, 417 pp, 1992.
Ericsson, T., A. Goransson, H. van Oene, and G. Gobran, Interactions
between aluminium, calcium and magnesium - Impacts on nutrition and
growth of forest trees, Ecolog. Bulletins, 44, 191-196, 1995.
Fox, S., and R. A. Mickler, eds., Impact of Air Pollutants on Southern
Pine Forests, Springer-Verlag, NY, Ecol. Studies, Vol. 118, 513 pp,
1996.
Gawel, J. E., B. A. Ahner, A. J. Friedland, and F. M. M. Morel,
Role for heavy metals in forest decline indicated by phytochelatin
measurements, Nature, 381, 64-65, 1996.
Haapala, H., N. Goltsova, R. Seppala, S. Huttunen, J. Kouki, J.
Lamppu, and B. Popovichev, Ecological condition of forests around the
eastern part of the Gulf of Finland, Environ. Pollut., 91, 253-265,
1996.
Hedin, L. O., L. Granat, G. E. Likens, T. A. Buishand, J. N.
Galloway, T. J. Butler, and H. Rodhe, Steep declines in atmospheric
base cations in regions of Europe and North America, Nature, 367,
351-354, 1994.
Heinsdorf, D., The role of nitrogen in declining Scots pine forests
(Pinus sylvestris) in the lowland of East Germany, Water, Air, and Soil
Pollut., 69, 21-35, 1993.
Hendershot, W., and A. R. C. Jones, Maple decline in Quebec: A
discussion of possible causes and the use of fertilizers to limit damage,
The Forestry Chronicle, 280-287, Aug. 1989.
Holopainen, J. K., A. Mustaniemi, P. Kainulainen, H. Satka, and J.
Oksanen, Conifer aphids in an air-polluted environment. I. Aphid
density, growth and accumulation of sulphur and nitrogen by Scots pine
and Norway spruce seedlings, Environmental Pollut., 80, 185-191,
1993.
Johnson, A. H., and T. J. Siccama, Acid deposition and forest decline,
Environ. Sci. Technol., 17, 294A-305A, 1983.
Katzensteiner, K., G. Glatzel, and M. Kazda, Nitrogen-induced
nutritional imbalances--a contributing factor to Norway spruce decline
in the Bohemian Forests (Austria), Forest Ecol. and Management, 51,
29-42, 1992.
Lambert, N. J., J. Ardo, B. N. Rock, and J. E. Vogelmann, Spectral
characterization and regression-based classification of forest damage in
Norway spruce stands in the Czech Republic using Landsat Thematic
Mapper data, Int. J. Remote Sens., 16, 1261-1287, 1995.
Lamersdorf, N. P., and M. Meyer, Nutrient cycling and acidification
of a northwest German forest site with high atmospheric nitrogen
deposition, Forest Ecology and Management, 62, 323-354, 1993.
Lawrence, G. B., M. B. David, and W. C. Shortle, A new mechanism
for calcium loss in forest-floor soils, Nature, 378, 162-165, 1995.
Likens, G. E., and F. H. Bormann, Acid rain: A serious regional
environmental problem, Science, 184, 1176-1179, 1974.
Likens, G. E., C. T. Driscoll, and D. C. Buso, Long-term effects of
acid rain: Response and recovery of a forest ecosystem, Science, 272,
244-248, 1996.
Little, Charles E., The Dying of the Trees, The Pandemic in America's
Forests, Viking Penguin, Penguin Books USA, Inc., 375 Hudson St.,
NY, NY 10014, ISBN 0-670-84135-8, 275 pp, 1995.
Lovett, G. M., Atmospheric deposition of nutrients and pollutants in
North America: An ecological perspective, Ecol. Applic., 629-650,
1994.
Lovett, G. M., and S. E. Lindberg, Atmospheric deposition and
canopy interactions of nitrogen in forests, Can. J. For. Res., 23, 1603-
1616, 1993.
Majumdar, S. K., J. R. Halma, S. W. Cline, D. Rieker, C. Daehler,
R. W. Zelnick, T. Saylor, and S. Geist, Tree ring growth and
elemental concentrations in wood cores of oak species in eastern
Pennsylvania: Possible influences of air pollution and acid deposition,
Environ. Technol., 12, 41-49, 1991.
Matzner, E., and D. Murach, Soil changes induced by air pollutant
deposition and their implication for forests in Central Europe, Water,
Air and Soil Pollut., 85, 63-76, 1995.
Nellemann, C., and T. Frogner, Spatial patterns of spruce defoliation:
Relation to acid deposition, critical loads, and natural growth conditions
in Norway, Ambio, 23, 255-259, 1994.
Nilsen, P., Effect of nitrogen on drought strain and nutrient uptake in
Norway spruce Picea abies (L.) Karst.) trees, Plant and Soil, 172, 73-
85, 1995.
Nilsson, S., and P. Duinker, The extent of forest decline in Europe,
Environment, 29(9), 4-9, 30-31, Nov. 1987.
Oleksyn, J., and K. Przybyl, Oak decline in the Soviet Union - scale
and hypothesis, European J. Forest Pathology, 17, 321-336, 1987.
Oleksyn, J., and P. B. Reich, Pollution, habitat destruction, and
biodiversity in Poland, Conservation Biology, 8, 943-960, 1994.
Ouimet, R., and C. Camire, Foliar deficiencies of sugar maple stands
associated with soil cation imbalances in the Quebec Appalachians,
Can. J. Soil Sci., 75, 169-175, 1995.
Persson, H., H. Majdi, and A. Clemensson-Lindell, Effects of acid
deposition on tree roots, Ecological Bulletins, 44, 158-167, 1995.
Phipps, R. L., and J. C. Whiton, Decline in long-term growth trends
of white oak, Can. J. For. Res., 18, 24-32, 1988.
Pitelka, L. F., and D. J. Raynal, Forest decline and acidic deposition,
Ecology, 70, 2-10, 1989.
Schmieden, U., and A. Wild, The contribution of ozone to forest
decline, Physiologia Plantarum, 94, 371-378, 1995.
Schulze, E.-D., W. De Vries, M. Hauhs, K. Rosen, L. Rasmussen,
C.-O. Tamm, and J. Nilsson, Critical loads for nitrogen deposition on
forest ecosystems, Water, Air, and Soil Pollut., 48, 451-456, 1989a.
Schulze, E.-D., R. Oren, and O. L. Lange, Nutrient relations of trees
in healthy and declining Norway spruce stands, Ch. 4-F in Schulze, E.-
D., O. L. Lange, and R. Oren, eds., Forest Decline and Air Pollution,
Ecological Studies 77, Springer-Verlag, New York, pp 392-417,
1989b.
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forests in Central Europe: Symptoms, development, and possible
causes, Plant Disease, 69, 548-558, 1985.
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deposition budgets for the United States and Canada, Water, Air, and
Soil Pollution, 63, 211-235, 1992.
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understanding how trees grow and defend themselves, Ann. Rev.
Phytopathol., 2, 189-214, 1984.
Shortle, W. C., and K. T. Smith, Aluminum-induced calcium
deficiency syndrome in declining red spruce, Science, 240, 1017-1018,
1988.
Shortle, W. C., and E. A. Bondietti, Timing, magnitude, and impact of
acidic deposition on sensitive forest sites, Water, Air, and Soil
Pollution, 61, 253-267, 1992.
Shortle, W. C., K. T. Smith, R. Minocha, and W. A. Alexeyev,
Similar patterns of change in stemwood calcium concentration in red
spruce and Siberian fir, J. Biogeography, 22, 467-473, 1995.
Sterba, H., Forest decline and increasing increments: A simulation
study, Forestry, 68, 153-163, 1995.
Stubbs, H. S., et al., Air Pollution and Forest Decline: Is There a
Link?, U.S. Dept. of Agriculture, Forest Service, AIB 595, 13 pp,
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Sverdrup, H., P. Warfvinge, and D. Britt, Assessing the potential for
forest effects due to soil acidification in Maryland, Water, Air and Soil
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Webb, S. L., and M. G. Glenn, Red spruce decline: A major role for
acid deposition, Ecology, 74, 2170-2071, 1993.
Woodman, J. N., and E. B. Cowling, Airborne chemicals and forest
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